Continuity mistake: When Ned executes the deserter, the wide leather straps of Ned's cloak are crisscrossed with his left over his right. But when Ned walks over to Bran, the straps are now crisscrossed the opposite way. Not due to flipped shots.
Continuity mistake: When Ser Barriston throws his armor and sword on the floor after being demoted, the sword stops by his armor. However when Sansa kneels down, the sword is now a good distance from the armor. (00:52:40)
Continuity mistake: When Catelyn meets up with Robb's forces, she hugs her son and then puts her hand on his shoulder/chest. In the next shot, her hand is down by her side. (00:41:40)
Continuity mistake: When Jon and the others emerge onto the other side of the wall, there are 4 people with torches. Pay attention to the one at the back on the screen left. He has his torch in his left hand in this shot, but as the shot changes to the front he now has his torch in his right hand. (00:44:30)
Cripples, Bastards, and Broken Things - S1-E4
Continuity mistake: When Ned and Petyr are walking and talking about Sir Hugh of the Vale, they pass a wheelbarrow while walking in a straight line that simply vanishes from the side of the path. (00:28:05)
Continuity mistake: Arya and Syrio are practising at the start, we see them stop with their swords touching and crossed. Camera changes and Syrio's sword is much lower and no longer touching Arya's. (00:02:10)
Continuity mistake: When Jon is taking his vow at the tree, the red markings on the tree change between shots. 2 single lines become joined, and a third single line becomes less smudged. (00:45:00)
Continuity mistake: When the group of men emerge at the other side of the wall, the last man with a torch has it held vertically. Camera cuts and now it is held at around a 45 degree angle. (00:44:30)
Continuity mistake: When Bran is asking about where his mother has gone he is playing with a lure. Between instant cuts the position of the lure in his hand is constantly changing. (00:15:20)
Continuity mistake: After the attack on Catelyn we see Bran Luwin and Theon talking while Theon is practising archery, the arrows in the board are constantly changing position and appearing and disappearing with no time to do so. (00:13:50)
Continuity mistake: Ser Jorah has just given Daenerys 3 books as her wedding present. As she takes them, their spines are pointing towards her right side. Cut to the next shot, as Jorah informs her that he served her father, the spines are now pointing towards her left side. (00:50:45)
Continuity mistake: When we see the dead deer at the start there are maggotts all over the face of the deer. Between camera angles, the position of the maggots differ drastically. (00:15:00)
Continuity mistake: When Tyrion wakes up inside the skycell you can see two skylights in the ceiling of the cell through which the sunlight passes. However, when we get a long shot of the skycells, you can see there's no way for the light to pass through them, as there are no "holes" on the floor of the cells above Tyrion's. (00:13:45)
Continuity mistake: When Ser Vardis has cornered Bron right at the edge of the moon door the position of Bron's body changes between shots. When the shot is taken from inside the moondoor, Bron's body leans backwards, over the moondoor. But when the shot is taken from behind the throne Bron is leaning forward.
Revealing mistake: Just after Jon is told he is confined to quarters, there is a shot of outside with snow falling. However the snow is actually rising. Indicating the shot has been reversed. (00:22:55)
Continuity mistake: Catelyn confronts her sister about the raven's message that arrived at dawn. When she does, the roll of paper is rolled completely differently between the 2 camera angles. (00:16:05)
Continuity mistake: When the guard is hitting Tyrion in the sky cell, Tyrion has his arms outstretched in one shot and against the wall in the next. (00:14:00)
Continuity mistake: Khal Drogo has just lifted Daenerys onto her horse after their wedding celebration. Her hair is behind both shoulders. In the immediate next shot, her hair has now moved in front. (00:55:00)
Continuity mistake: When King Robert arrives at Winterfell, the wide leather straps of his cloak are crisscrossed with his left over his right, but when Robert and Ned walk inside the crypts, Robert's straps are crisscrossed the opposite way, with his right over his left. The shots are not flipped.
Chosen answer: Considering the show was in production for nearly a decade, it is hardly surprising that many characters were recast. Actors constantly move on to other jobs, creating scheduling conflicts. Some may not want to be tied to one project for so long a period, particularly for relatively minor roles that paid little money. As some characters became more prominent, the producers did recast a few roles with better-known actors. For example, Max Von Sydow replaced the actor who originally played the Three-eyed Raven. Some actors voluntarily left for personal reasons. Jennifer Ehle was originally cast to play Catelyn Stark but dropped out because she'd recently given birth. Other actors claimed they were replaced for "political" reasons. Here is a website with a rundown of which actors were replaced and why: https://screenrant.com/game-thrones-characters-recast-new-actors-every-why/.
raywest ★